The Spear Pillar is a set of ruins located on the peak of Mt. Coronet. The ruins here provide access to the different dimensions of the universe and serve as portals for Dialga, Palkia and Giratina to access the real world. As such, Team Galactic's plans come to fruition in this area where you have to stop them and tame the Pokémon for each respective game. In Platinum, you can return here with the Adamant Orb and Lustrous Orb to access portals to get you Dialga & Palkia. Spear Pillar also serves as the gateway to the Hall of Origin